Abstract

Near coasts, surface water–groundwater interactions control many biogeochemical processes associated with the critical zone,
which extends from shallow aquifer to vegetative canopy. For example, submarine groundwater discharge delivers a significant
fraction of weathering products such as silica and calcium to the world's oceans. Owing to changing fertilizer and land use
practices, submarine groundwater discharge is also responsible for high nitrogen loads that drive eutrophication in marine
waters. Submarine groundwater discharge is generally unmonitored due to its heterogeneous and diffuse spatial patterns and
complex temporal dynamics. Here, we review the physical processes that drive submarine groundwater discharge at various spatial
and temporal scales and highlight examples of interdependent critical zone processes. Like the inland critical zone, the coastal
critical zone is undergoing rapid change in the Anthropocene. Disturbances include warming air and sea temperatures, sea‐level
rise, increasing storm severity, increasing nutrient and contaminant inputs, and ocean acidification. In a changing world,
it is more important than ever to understand complex feedbacks between dynamic surface water‐groundwater interaction, rocks,
and life through long‐term monitoring efforts that extend beyond inland rivers to coastal groundwater. WIREs Water 2016, 3:706–726. doi: 10.1002/wat2.1157

This article is categorized under:

Water and Life > Nature of Freshwater Ecosystems

Science of Water > Water and Environmental Change

Science of Water > Water Quality

Images

Effect of ocean surges on the critical zone. (a) Photograph of coastal Thailand 3 weeks after the 2004 Indian Ocean tsunami. Saline floodwater is still visible in surface depressions. (b) Schematic of infiltration of saline floodwater into a fresh aquifer and associated changes in chemistry and mobilization of trace metals.